The present invention relates to brushless direct current (DC) motors and, more particularly, to a stator structure and method of manufacture of a claw-pole stator structure for such motors.
One form of brushless DC motor includes a stator structure comprising a pair of opposed, complementary, claw-pole stator members with a stator winding formed on a bobbin and sandwiched therebetween. Each of the stator members comprises a planar base component with a plurality of circumferentially spaced stator poles extending in a normal direction from adjacent a periphery of the base component. A central core member extends from at least one of the base components of each pair and passes through a center of the winding bobbin. A permanent magnet rotor circumscribes the stator structure and is radially spaced therefrom by a small air gap.
Prior art methods of manufacture of claw-pole stators include machining the complementary stator pairs from solid blocks of ferromagnetic material, typically a block of molded magnetic material such as a powdered iron in a plastic matrix. While this method produces a structure with good electrical and magnetic characteristics, the cost of manufacture is generally excessive. Another method that is more economically viable is to form the stator structure by stamping a magnetic metal plate and then bending circumferential extensions of the plate to form the depending magnetic poles. In general, such stamped and bent structures have unsatisfactory electrical and magnetic characteristics. Accordingly, it is desirable to provide a clawpole, brushless DC motor and method of manufacture which is both economical and has good electrical and magnetic characteristics.